using System;

using System.Data;

public class Program

{

    public static void Main()

    {

        DataTable dt = new DataTable();

        dt.Columns.Add("StartTime", typeof(System.TimeSpan));

        dt.Columns.Add("StartTimeString", typeof(System.String), "convert(StartTime, 'System.String')");    //this calculated column was added just to see what was going on

        DataRow dr = dt.NewRow();

        dr["StartTime"] = DateTime.Now.TimeOfDay;

        /* set the filter time */

        TimeSpan FilterTime = new TimeSpan(0, 20, 15, 0, 0);    

        Console.WriteLine(string.Format("FilterTime formated: {0}",FilterTime.ToString("'PT'hh'H'mm'M'ss'.'fffffff'S'")));

        dt.Rows.Add(dr);

        // wow, convert in a sql expression generates a weird format

        Console.WriteLine(string.Format("Row 0 StartTime formated: {0}", dt.Rows[0]["StartTimeString"]));

        dt.DefaultView.RowFilter = string.Format("convert(StartTime, 'System.String') < '{0}'", FilterTime.ToString("'PT'hh'H'mm'M'ss'.'fffffff'S'"));

        Console.WriteLine(string.Format("# of rows before the filter time: {0}", dt.DefaultView.Count.ToString()));

    }

}